Cyanobacteria (blue-green algae)

Kejimkujik National Park and National Historic Site

Parks Canada is advising visitors that cyanobacteria (commonly referred to as blue-green algae) may be present in lakes, rivers and streams in Kejimkujik National Park and National Historic Site. The presence and abundance of cyanobacteria varies by season. In general, cyanobacteria bloom in aquatic ecosystems between May and October.

What are cyanobacteria?

Cyanobacteria are aquatic microorganisms found naturally in aquatic environments. Their pigmentation can vary from blue-green, olive green, dark green, purple to red. The presence of cyanobacteria in aquatic ecosystems is normal, but it can become a problem when they multiply rapidly and form a mass visible to the naked eye on the water surface. This is known as a "bloom." Clusters of cyanobacteria are then formed on the surface, called "blooms," foam or froth, depending on their intensity.

Several species of cyanobacteria store natural poisons called cyanotoxins in their cells. These toxins are released into the water when the cells break down or die. Contact with or ingestion of water contaminated with too much cyanotoxin can cause health problems for people and animals.

Identify cyanobacteria

The visible blooms are most often green or turquoise and depending on their intensity look like:

abnormally cloudy water, floating particles or thin streaks on the surface. Low-density blooms may not necessarily give the impression of a change in the water
a "soup" of particles, similar to pea soup, or filaments that look like thin, short pieces of grass
a paint spill on the surface or a film on the surface of the water or coloured deposits near the shore

Images of cyanobacteria blooms

Floating green particles in shallow water. — Cloudy water and floating particles

A soupy green lake surface with a forested background. — Algae blooms that form a soup of particles

Cyanobacteria particles form a film on the water surface. — Algae blooms that form a film on the surface of the water

Conditions for the spread of cyanobacteria

Cyanobacteria need light, heat and nutrients to grow. When the conditions are right, they can spread rapidly throughout a body of water. Many factors influence their growth; as a result, it is hard to predict the timing of cyanobacteria blooms. But some conditions are more likely to produce blue-green algae:

water rich in nutrients (mainly phosphorus)
stagnant water
light intensity
a sudden increase in ambient temperature

Effects of cyanobacteria

Cyanobacteria blooms can have multiple consequences.

Impacts of cyanobacteria on ecosystem health

Ecosystem nutrient imbalance
Oxygen depletion
Mass mortality of fish, invertebrates and animals (by ingestion of toxins)

Impact on human and animal health

Exposure to cyanotoxins, by consumption or by direct or indirect contact, can lead to gastro-enteritis and/or liver and kidney disorders. While there are no recorded deaths in humans linked to contact with blue-green algae, it has been fatal to dogs and cattle who have ingested the toxin.

Possible symptoms include:

digestive disorders (stomach-ache, nausea, vomiting, diarrhea, etc.)
neurological disorders (dizziness, headache, malaise, fever, etc.)
skin disorders (itching, irritation, redness, etc.)

Symptoms may vary from one person to another, depending on the concentration of toxins present and the conditions of exposure.

Prevention and actions to take

In areas affected by blue-green algae blooms, it is recommended to:

avoid water-based activities that may result in direct contact with cyanotoxins
avoid areas with concentrations of blue-green algae
keep at least 3 metres away from blooms or foam
keep young children away from potentially contaminated areas
keep pets on a leash, to avoid access to the affected body of water
NOT consume any fish caught in the affected body of water
NOT drink water directly from a contaminated water body

What to do in case of contact with cyanobacteria

Avoid touching your face with your hands
Wash your hands or other affected body parts thoroughly before touching your eyes, face or mouth and before eating, drinking or smoking
Thoroughly wash any objects or equipment that have come into contact with the contaminated water

If symptoms occur as a result of contact with cyanobacteria, seek medical attention.

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